TWI569557B - Charging control method for rechargable battery - Google Patents

Description

Charging battery charging control method

The present invention relates to a charging control method for a rechargeable battery, and more particularly to a charging control method that utilizes a balancing circuit and a charging current adjustment measure to uniformly charge each battery cell of the rechargeable battery.

The conventional rechargeable battery is charged in three modes: precharge mode, fast charge mode and constant voltage mode. When the precharge mode is first, the cells of the rechargeable battery are charged in a low current manner. When the voltage of each cell reaches a first transition voltage, enter the fast charge mode and charge the cells with a large current until the voltage of one of the cells reaches a second transition voltage. Enter the constant voltage mode, and then charge each battery cell in a constant voltage.

In the manufacturing process of the conventional rechargeable battery, although the battery cells are pre-screened and assembled, however, the characteristics of the battery cells, especially the internal resistance, are difficult to control to be completely the same. The existing charging method can easily lead to an outlier phenomenon in the voltage difference between the cells, so that the voltage difference between the cells becomes larger. As a result, some of the cells will be fully charged when the battery is being charged, and the other cells will not be fully charged, so that the user cannot effectively utilize all the battery capacity. In addition, this phenomenon will become more apparent as the number of battery charges continues to increase.

Taiwan Patent No. I343141 discloses a method of charging a battery, please refer to Fig. 5 of the drawings. The patent first performs constant current charging with a first preset current I ₁ and detects the voltage of each battery parallel group of the battery module. Then, when one cell reaches a first predetermined set of parallel voltage value V _1, the current of the cell cut in parallel to a second group of predetermined current I _2, and when this group was returned to the batteries in parallel When the first preset voltage value V ₁ is determined, it is judged that the power of the parallel group of the cells is almost full. However, the above patent does not describe how to cut a first predetermined voltage value V a current cell of _a parallel group of arrival.

In addition, a charging method is also disclosed in the Japanese Patent No. 103532191A, please refer to FIG. 1 of the drawings. The first battery pack and the second battery pack are in parallel relationship and are connected to the power source 5 through the switching power supply. In addition, the patent uses a voltage detecting device to detect the voltage values of the first battery pack and the second battery pack. When the difference between the voltages is too large, the charging processor adjusts the charging current to make the battery pack with a lower voltage. The charging current is greater than the charging current of the battery pack with a higher voltage.

The above patents are mainly directed to battery packs connected in parallel, and do not provide any technical solution for the charging mode of the battery packs connected in series.

Compared with the prior art, the present invention provides a new charging control method for a rechargeable battery, which can reduce the voltage difference between the cells in series when charging in the fast charging mode.

In order to achieve the above object, the present invention provides a charging control method for a rechargeable battery, which includes the following steps in a fast charging mode: step a) charging a rechargeable battery, the interior of the rechargeable battery including a plurality of serial connections The cells are respectively connected to a balancing circuit to be switched between a closed state and an open state, and consume the electrical energy connected to the battery in the closed state; and step b) measuring each battery Voltage; and step c) judging the cell Whether the difference between a maximum voltage value and a minimum voltage value of the voltage value is less than a critical value, and if the determination result is yes, controlling the balancing circuit to be in an open state and returning to step b), otherwise the control corresponds to having The balance circuit of the maximum voltage value is in a closed state, and the other balance circuit is in an open state, and the current value of the charge current is adjusted to be equal to the calculated value obtained by dividing the maximum voltage value by the impedance value of the balance circuit.

Therefore, in the charging process of the fast charging mode, if the voltage difference between the cells is found to be too large, the balance circuit can be controlled to maintain the voltage of the cell having the largest voltage value at a constant value, and let other cells Continue charging and the voltage value continues to increase, thereby controlling the difference between all the cell voltages within the critical value, so that the cell can be fully charged during the charging process.

The charging control method of the present invention has at least the following two advantages:

Advantage 1: The battery-connected rechargeable battery is mostly provided with a balancing circuit to avoid the problem that some cells are overcharged during charging. The charging control method of the present invention utilizes an existing balancing circuit to reduce the voltage difference between the cells, without the need to additionally add other hardware components, and thus does not increase the hardware cost.

Advantage 2: The charging control method of the invention allows each battery core to reach a deep charge in a balanced manner, which not only prolongs the use time of the rechargeable battery, but also maintains the life of the rechargeable battery.

1‧‧‧Battery charging module

10‧‧‧Rechargeable battery

12‧‧‧Balance circuit

121‧‧‧Switch

122‧‧‧ Consumption resistance

13‧‧‧First battery

14‧‧‧second battery

△V‧‧‧ difference

20‧‧‧Microcontroller

30‧‧‧Charger

I‧‧‧Precharge mode

II‧‧‧ fast charge mode

III‧‧ ‧ constant voltage mode

S1.1-1.18‧‧‧Steps

T1‧‧‧ first transition voltage

T2‧‧‧second transition voltage

1 is a schematic diagram of a hardware structure of a battery charging module according to a preferred embodiment of the present invention; FIG. 2a is a flow chart of steps according to a preferred embodiment of the present invention; FIG. 2b is a flow chart of steps following FIG. 2a; The figure is a flow chart of the steps following the 2a figure; 3 is a diagram showing changes in charging current and cell voltage versus time of a rechargeable battery during charging according to a preferred embodiment of the present invention; and FIG. 4 is a charging current and a cell voltage pair when the rechargeable battery of the control group is being charged. Time change chart.

In order to better understand the features of the present invention, the present invention provides a preferred embodiment and is described below in conjunction with the drawings. Please refer to Figures 1 to 4. The same or similar elements will be used in the following embodiments to facilitate identification.

The rechargeable battery 10 in the present specification may be at least one of, but not limited to, a lithium battery, a nickel hydrogen battery, and a lead acid battery.

Referring first to the hardware architecture diagram of the battery charging module of FIG. 1, the battery charging module 1 includes a rechargeable battery 10, a microcontroller 20, and a charger 30. The charging battery 10 includes two first batteries 13 and a second battery 14 connected in series. The first battery 13 and the second battery 14 are connected to a balancing circuit 12 . The balancing circuit 12 of the present embodiment includes a switch 121 and a consuming resistor 122. The positive voltage terminals of the first battery core 13 and the second battery core 14 are both coupled to one end of the switch 121 of the corresponding balancing circuit 12 thereof, and The two ends of the consuming resistor 122 are respectively connected to the other end of the switch 121 and the negative terminals of the first core 13 and the second core 14, so that the impedance value of the balancing circuit 12 is substantially equal to the impedance value of the consuming resistor 122. It should be noted that the number of cells of the rechargeable battery 10 may be two or more, which is not limited to the embodiment.

The microcontroller 20 includes a general-purpose input and output (GPIO) to perform input and output of signals, and is electrically connected to a positive voltage terminal and a negative voltage terminal of the first battery cell 13 through, for example, an analog-to-digital converter (ADC) interface. Connecting the positive voltage terminal and the negative voltage terminal of the second battery core 14 for measuring The voltage values of the first cell 13 and the second cell 14 are measured. In addition, the microcontroller 20 controls and controls the charger 30 by, for example, an internal integrated circuit (I2C) or a serial peripheral interface (SPI). On the other hand, the microcontroller 20 controls the switch 121 of each balancing circuit 12 through the aforementioned general-purpose output input (GPIO) interface, and controls the balancing circuit 12 to be in a closed state and an open state by controlling the conduction of the switch 121. Switch between.

The charger 30 is controlled by the microcontroller 20 to supply power to the first cell 13 and the second cell 14 of the rechargeable battery 10, and is capable of performing a precharge mode, a fast charge mode, and a constant voltage mode.

The hardware architecture of this embodiment has been described. The steps of the charging control method of the rechargeable battery will be described in detail below. Please refer to FIGS. 2a to 3 .

Please refer to Figures 2a and 3 first. In step S1.1, the rechargeable battery 10 starts to be charged. At this time, the voltage values of the first battery core 13 and the second battery core 14 in this embodiment are both lower than a first transition voltage T1 (refer to FIG. 3). The charger 30 is charged in a precharge mode I (step S1.2) with a charging current of, for example, 0.1 ampere.

Then, in step S1.3, the microcontroller 20 measures the voltage values of the first cell 13 and the second cell 14, and performs step S1.4 to determine the voltage values of the first cell 13 and the second cell 14. Whether the first transition voltage T1 is reached or exceeded, if the determination result is yes, the microcontroller 20 will control the charger 30 to charge in the fast charge mode II (step S1.5); otherwise, return to step S1.2. , maintaining charging in the precharge mode I.

In the fast charge mode II, the charger 30 will increase the current value of the charging current (for example, 1 amp) to charge the first cell 13 and the second cell 14. Then, proceeding to step S1.6, the microcontroller 20 measures the voltage values of the first cell 13 and the second cell 14, and proceeds to step S1.7 to determine whether any of the cell voltage values reach the second transition voltage. T2, if the judgment result is yes, enter the step S1.12, otherwise proceed to step S1.8.

In step 1.8, the microcontroller 20 will re-measure the maximum voltage value and the minimum voltage value among the voltage values of the first battery core 13 and the second battery core 14, and calculate the difference between the maximum voltage value and the minimum voltage value. The value is ΔV, and it is judged whether or not the difference ΔV is smaller than a critical value. If the result of the determination is YES, the balance circuit is controlled to be in an open state and return to step S1.5 to continue charging in the fast charge mode II; otherwise, the process proceeds to step S1.9.

In this embodiment, the threshold value is set to 3% of the State Of Charge (SOC), but is not limited thereto.

Please refer to Figure 2b and Figure 3. In step S1.9, the embodiment assumes that the voltage value of the first battery core 13 is greater than the voltage value of the second battery core 14, and the difference ΔV between the maximum voltage value and the minimum voltage value is greater than a critical value. The microcontroller 20 controls the balancing circuit 12 of the first battery core 13 and the second battery core 14 in a closed state and an open circuit state, respectively, and adjusts the current value of the charging current to be equal to the voltage value of the first battery core 13 (ie, the maximum voltage value). Divided by the calculated value obtained by consuming the resistance value of the resistor 122. At this time, the electric energy of the first battery core 13 is consumed by the consumption resistor 122 due to the conduction of the switch 121, so that the voltage of the first battery core 13 does not rise any more, and the voltage value of the second battery core 14 continues to increase, thereby The voltage values of the first cell 13 and the second cell 14 can be gradually reduced to approach the same.

Step S1.9 is continued, and the voltage values of the first cell 13 and the second cell 14 are measured in step S1.10, and then the voltage values of the first cell 13 and the second cell 14 are determined in step S1.11. Whether the difference ΔV is equal to zero. If the difference ΔV is not equal to 0, the process returns to step S1.9; otherwise, the process returns to step S1.5 to restore the maximum current value of the charging current in the fast charge mode and continue charging.

Please refer to FIG. 2c. If the voltage value of any one of the cells reaches the second transition voltage T2 (following step S1.7), regardless of whether the difference ΔV between the first cell 13 and the second cell 14 is If it is less than the critical value, it proceeds to step S1.12. Wherein, in step S1.12, it is assumed that the first cell 13 has reached the second transition voltage T2 and the second cell 14 has not reached the second transition voltage T2, at which time the balancing circuit of the first cell 13 will be turned on. The switch 121 of 12 switches to the closed state, and the remaining balance circuit 12 is in an open state, and adjusts the current value of the charging current to be equal to the voltage value of the first core 13 of the higher voltage (ie, the second transition state) The voltage T2) is divided by the calculated value obtained by consuming the impedance value of the resistor 122. At this time, the electric energy of the first battery core 13 will be consumed by the consumption resistor 122 due to the conduction of the switch 121, so that the voltage value of the first battery core 13 will be maintained at the second transition voltage T2, and the voltage of the second battery core 14 The value continues to rise.

Then, the process proceeds to step S1.13, and the voltage values of the first cell 13 and the second cell 14 are measured, and the process proceeds to step S1.14 to determine whether the difference between the voltage values of the first cell 13 and the second cell 14 is equal to 0, if the difference is not equal to 0, then return to step S1.12, and then repeat steps S1.13 and S1.14 until the difference between the voltage values of the first cell 13 and the second cell 14 is equal to 0, That is, after the voltage values of both of them reach the second transition voltage T2, the process proceeds to step S1.15.

In step S1.15, the microcontroller 10 will control the charger 30 to be charged in the constant voltage mode III. In this embodiment, the current value of the charging current will drop (as in Fig. 3). Then, the voltage values of the first cell 13 and the second cell 14 are measured in step S1.16, and the process proceeds to step S1.17 to determine whether any of the first cell 13 or the second cell 14 reaches the cutoff voltage. . If none of the first cell 13 or the second cell 14 reaches the cutoff voltage, step S1.15 to step S1.17 are repeatedly performed; otherwise, the microcontroller 20 controls the charger 30 to stop charging (step S1. 18), to avoid danger when the battery 10 is overcharged.

In the above embodiment, once the microcontroller 20 finds that the difference ΔV of the voltage between the cells is too large, the balance circuit 12 corresponding to the cell having the largest voltage value can be controlled. In the closed state, and adjusting the current value of the charging current, the voltage of the cell having the largest voltage value is maintained at a constant value, and the voltage values of other cells are continuously increased to balance the state of charge of each cell.

Fig. 4 is data of a battery module using a conventional charging method as a control group, from which it can be seen that after entering the fast charging mode II, the voltage difference ΔV between the cells gradually expands, so that the state of charge of the two There is a significant difference, and the entire rechargeable battery cannot be deeply charged. As a result, after a plurality of charge and discharge cycles, if a part of the cells cannot be deeply charged, the life of the rechargeable battery 10 may be shortened.

It should be noted that during the charging process, the cell having the largest voltage value and the cell of the minimum voltage value may be changed at different time points, and thus should not be limited by the embodiment.

Finally, it should be noted that the implementation steps disclosed in the foregoing embodiments are merely illustrative and are not intended to limit the scope of the present invention. Other possible alternative changes are also covered by the scope of the patent application of the present application. .

S1.5, S1.8-S1.11‧‧‧ steps

Claims (7)

A charging control method for a rechargeable battery, characterized in that in a fast charging mode, the method comprises the following steps: a) charging a rechargeable battery, the rechargeable battery internally comprising a plurality of cells connected in series, each of the cells Correspondingly, a balancing circuit is respectively connected, and each of the balancing circuits can switch between a closed state and an open state, and consume the electrical energy connected to the battery in the closed state; b) measure the voltage values of the cells; c) determining whether the difference between a maximum voltage value and a minimum voltage value of the voltage values of the cells is less than a threshold value, and if the determination result is yes, controlling the balancing circuit to be in an open state and returning to step b) And vice versa; and d) controlling the balancing circuit corresponding to the battery cell having the maximum voltage value in a closed state, and the other balancing circuit is in an open state, adjusting a current value of the charging current to be equal to the The calculated value of the maximum voltage value divided by the impedance value of the balancing circuit. The charging control method of claim 1, wherein each of the balancing circuits includes a switch electrically connected and a consuming resistor, and the switch and the consuming resistor are respectively electrically connected to a positive voltage end of the corresponding battery core. And a negative voltage terminal; wherein the impedance value of each of the balancing circuits is substantially equal to the impedance value of the consumable resistor. The charging control method according to claim 1 or 2, wherein after adjusting the current value of the charging current in step d), further comprising performing a step d1) re-measuring and determining a maximum voltage value of the voltage values of the cells Whether the difference from a minimum voltage value is equal to 0, if the result of the determination is yes, then return to step b), otherwise, return to step d). The charging control method of claim 3, wherein the step b) further comprises determining whether a voltage value of any of the cells reaches a second transition voltage, and if the determination result is no, performing step c), Otherwise, step d2) is performed, so that the balance circuit corresponding to the cell that reaches the second transition voltage is in a closed state, and the remaining balance circuits are in an open state, and the current value of the charging current is adjusted to be equal to the cells. The voltage maximum value is divided by the impedance value of the balance circuit; after step d2) is completed, step d3) is performed to re-measure and determine the difference between a maximum voltage value and a minimum voltage value of the voltage values of the cells. Whether the value is equal to 0, if the result of the determination is no, then return to step d2), otherwise, perform a step e) to charge the rechargeable battery in a certain voltage mode. The charging control method according to claim 4, wherein the step e) further comprises a step e1) measuring the voltage of each of the cells, and determining whether any of the cells reaches a cutoff voltage, and if the result is Yes, stop charging, otherwise return to step e). The charging control method according to claim 1, wherein in the step c), the threshold is equal to 3% of the state of charge of the cells. The charging control method according to claim 1, further comprising the step of performing a pre-charging mode before entering the fast charging mode, and when charging the cells in the pre-charging mode, measuring and determining the Whether the voltage value of the equalizing core reaches or exceeds a first transition voltage, and if the judgment result is yes, the fast charging mode is entered, and otherwise the precharge mode is maintained.